Additive to improve flow, reduce power consumption and pressure drop in heavy oil pipelines

ABSTRACT

A drag reducing additive for heavy oil, such as crude oil, includes a polymeric alkyl-substituted phenol formaldehyde resin and a solvent having at least one of an ester (e.g. ethyl acetate), an aldehyde (e.g. butyraldehyde), and an aromatic hydrocarbon (e.g. toluene, xylene, and the like), or mixtures thereof. When used together with a diluent (e.g. condensate, naphtha, or the like), the additive may reduce viscosity of the combined oil, diluent, and additive by at least 20%, increase throughput by at least 6%, reduce power consumption by at least 3%, reduce the diluent proportion by at least 3%, or some combination of these effects, as compared with an otherwise identical heavy oil without the additive.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/092,114 filed Aug. 27, 2008.

TECHNICAL FIELD

The invention relates to methods and compositions for reducing the dragof heavy oils, such as crude oils, and most particularly relates, in onenon-limiting embodiment, to methods and compositions for treating heavyoils to reduce viscosity, increase throughput, reduce power consumption,and/or reduce the diluent proportion thereof as they are beingtransported through a conduit such as a pipeline.

TECHNICAL BACKGROUND

Seventy percent of the world's known oil reserves are non-conventionalincluding heavy oil, extra heavy oil, and bitumen. These oils' highviscosities present a challenge in transporting them through pipelines.Traditionally, producers have used large quantities of condensate as adiluent to reduce the viscosity and make these oils more pumpable. Thecondensate is typically evaporated and pumped back to the productionsite via separate pipelines. With rising oil and gas prices, thesecondensates have become very expensive and their availability has becomelimited. The energy required to evaporate the condensate from the heavyoil and for its transmission back to the production site has also becomeincreasingly expensive. Thus, there is a significant economic incentiveto find methods and compositions to improve the efficiency oftransmitting heavy oils via pipelines.

Drag reducers are well known to be added to crude oil being transportedthrough pipelines to reduce the drag of the oil being pumpedtherethrough to enhance throughput, reduce pressure drop, reduce thepower requirements and thus the cost of operating the pipelines. Thesematerials can take various forms, including certain polymers in oilsoluble suspensions, emulsions, pellets, gels, microfine powders andparticulate slurries. High molecular weight polymers to reduce thefriction pressure loss in pipelines are used in a wide variety ofapplications. Different families of pipeline drag reducers have beendeveloped for optimal performance in different fluid types and undervarious pipeline conditions. Very high molecular weightpolyalpha-olefins are often used as drag reducers for crude oils.However, polyalpha-olefins are subject to shear degradation as the dragreducer and the oil are pumped through successive pumping stations, andthus tend to lose their effectiveness over time and distance. They (i.e.high molecular weight polyalpha-olefin drag reducers) are also used inpipelines with turbulent flow only.

It would be desirable if new methods and compositions for improving flowof heavy oils, such as heavy crude oils and bitumens, for instance byreducing power consumption and pressure drop, particularly if anadditive could be used that is not shear degraded over time anddistance, or is degraded to a lesser extent than more conventionalpolyalpha-olefins. Further, it would be desirable to discover newcompositions and methods that may be used in all flow regimes—laminar,transition to turbulence, and turbulent flow regimes.

SUMMARY

There is provided, in one non-limiting embodiment, a drag reducingadditive that includes a polymeric alkyl-substituted phenol formaldehyderesin, and a solvent that in turn contains an ester, an aldehyde, anaromatic hydrocarbon and/or mixtures thereof.

Additionally there is provided in an alternative non-restrictiveembodiment, a method of improving the flow of oil through a conduit. Themethod involves introducing to the oil an amount of a drag reducingadditive effective to improve the flow of oil through the conduit. Theadditive includes a polymeric alkyl-substituted phenol formaldehyderesin and a solvent. Again, the solvent contains at least one of anester, an aldehyde, an aromatic hydrocarbon or a mixture thereof.

In still another non-limiting embodiment, there is provided an oilhaving improved flow through a conduit. The improved oil includes an oil(e.g. a heavy oil or bitumen), a diluent, and an effective amount of adrag reducing additive. The drag reducing additive contains a polymericalkyl-substituted phenol formaldehyde resin and a solvent as previouslydescribed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph presenting the viscosity reduction capabilities offive formulations herein added to a diluted heavy oil;

FIG. 2 is a graph showing the improvement in flow due to the fiveadditives of FIG. 1 after testing in a flow loop;

FIG. 3 is a graph showing the reduction in power due to the fiveadditives of FIG. 1 after testing in a flow loop; and

FIG. 4 is a graph of the gain in transmission efficiency in a heavy oildue to the five additives of FIG. 1 after testing in a flow loop.

DETAILED DESCRIPTION

An additive has been discovered that reduces the viscosity of highviscosity crude oils and hence enhances their transmission throughpipelines. The additive increases the throughput of pipelines, reducespressure drop across pipelines and/or reduces the power consumed by thepumps used for pumping the crude oil along the pipelines. It alsoreduces the amount of diluent added to heavy oils to facilitate theirtransmission in pipelines.

More particularly, the drag reducing additive involves a formulation ofa polymeric alkyl-substituted phenol formaldehyde resin in a solvent orsolvent mixture containing an ester, an aldehyde, and/or an aromatichydrocarbon in the proportion of from about 1 to about 20 weight percentresin, with the balance being the solvent or solvent package.Alternatively, the proportion of resin in the drag reducing additiveranges from about 5 independently to about 7 wt % or even to about 10 wt%. The formulation is applied to the heavy oil at a dose rate of fromabout 0.1 to about 2 percent by volume; alternatively from about 0.1independently up to about 1 vol %.

In the polymeric alkyl-substituted phenol formaldehyde resin, the alkylsubstituent may be branched or linear from C₂ to C₂₀, alternatively fromC₇ independently to C₁₂ (by “independently” is meant that otheralternate ranges include, but are not necessarily limited to, C₂-C₁₂ andC₇ to C₂₀). Indeed, in one non-limiting embodiment, branched alkylsubstituents are particularly suitable because the branching givesbetter solubility characteristics, particularly at lower temperatures,which is very desirable since the resin may separate from the solventmixture at certain low temperature conditions.

The polymeric alkyl-substituted phenol formaldehyde resin may have aweight average molecular weight of from about 1500 to about 30,000, witha particularly suitable molecular weight range being from about 2000independently up to about 7000. As the molecular weight of the resinbecomes large, the viscosity of the ensuing drag reducing additivebecomes too high for them to be easily pumpable. Thus, in somenon-restrictive respects, a relatively lower molecular weight resin ismore suitable. These resin molecular weights are lower than the typicalmolecular weight ranges of more conventional polyalpha-olefin dragreducers, which because of their very high molecular weights and highviscosities have difficulty being efficiently introduced intohydrocarbon flows.

As a peculiarity of the method and composition herein, the solvent,solvent package or mixture is chosen such that none of the solventcomponents will end up in the jet fuel fraction of refinery productstreams. For pipeline transportation to be possible, the petroleumstream being transported should meet a viscosity specification of 350Centistokes or lower at 11.9 degrees Celsius, thus the heavy oil orbitumen is expected to have already been diluted with 10 to 30 volumepercent of a diluent such as condensate or naphtha or the like prior tothe addition of the drag reducing additive herein. The additive willthen enhance the solvency characteristics of the naphtha or condensatebeyond what is possible without the additive. Diluents may also includelight crude oil, light synthetic crude oil and other light petroleumhydrocarbon fractions.

The ester component may be present in the solvent mixture in an amountbased on the total solvent mixture (not the total drag reducingadditive) of from about 10 to about 95 wt %, alternatively from about 45independently to about 70 wt %. Suitable esters include, but are notnecessarily limited to, ethyl formate, methyl formate, methyl acetate,ethyl acetate, ethyl propionate, dimethyl carbonate, diethyl carbonate,ethyl lactate, and the like and mixtures thereof. Other esters such asbenzoates do improve the flow of the heavy oil, but they are notpreferred because they will end up in the jet fuel fraction of therefinery fuels and thus will not be permitted by the refineriesdownstream.

The aldehyde component may also be present in the solvent mixture in anamount based on the total solvent mixture of from about 10 to about 95wt %, in another non-restrictive version from about 20 to about 95 wt %,alternatively from about 45 independently to about 70 wt %. Suitablealdehydes include, but are not necessarily limited to, formaldehyde,acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, and the likeand mixtures thereof.

The aromatic hydrocarbon component of the solvent mixture may be presenttherein in an amount ranging from about 10 to about 95 wt %,alternatively from about 25 independently to about 50 wt %. Suitablearomatic hydrocarbons include, but are not necessarily limited to,toluene, xylene, refinery aromatic cuts boiling in a range from about320-350° F. (about 160-177° C.), and the like and mixtures thereof.

The solvent or solvent mixtures may contain components other than thesethree, such as alcohols, e.g. isopropyl alcohol as one non-limitingexample, but in most implementations it is preferred that the solventnot be one that is objectionable in the jet fuel fraction of adownstream refinery.

The drag reducing additive herein when used as described is capable ofreducing the viscosity of the diluted heavy oil or bitumen by 20 percentor more, increasing throughput by 6 percent or more and reducing powerconsumption by 3 percent or more. The compositions and methods may alsoreduce diluent use by 3 percent or more. Thus, the methods andcompositions described herein give the shipper or the pipeline companythe option of selecting which performance characteristic—increased flowor throughput, reduced power, reduced pressure drop, or reduction indiluent proportion to focus on, depending on existing conditions botheconomic and physical. Indeed, multiple advantages may be achieved,although if multiple advantages are desired, the level of improvementfor each advantage would not be expected to be the same as if only oneof the advantages were optimized.

The drag reducing additives described herein are expected to be usefulin any heavy oil, such as extra heavy crude oil or bitumen, or oils withhigh bitumen contents, or the like. There is no special or preferredmethod of introducing the drag reducing additives into the oil. Othercommon components may be added to the oil, for instance other flowimprovers or drag reducers. However in one non-limiting embodiment, thedrag reducing additive herein has an absence of a hydrophilic-lipophilicvinylic polymer.

The invention will now be described with respect to specific exampleswhich are not intended to limit the scope of the invention in any way,but to more fully illuminate and illustrate it.

Examples 6, 9, 10, 11 and 15

Five formulas were tested on a crude oil which was a Canadian bitumendiluted with between 25-30 vol % naphtha diluent. The naphtha was about60/40 vol/vol aliphatic/aromatic hydrocarbons. The five formulae had thecompositions set out in Table I:

TABLE I Test Formulae - Wt % Formula 9 10 6 11 14 Polymericalkyl-substituted phenol 5 5 5 5 5 formaldehyde resin Solvent mixtureEthyl acetate, wt % — 47.5 — 95 85 Butyraldehyde 47.5 — — — — Toluene47.5 47.5 95 — — Isopropyl alcohol — — — — 10

FIG. 1 shows the viscosity reduction capabilities of variousformulations in the methods herein. FIGS. 2 to 4 show the performance ofthe various additives in a flow loop. At a dose rate of 1 percent, theformulation can increase the flow and reduce the power consumed to pumpthe heavy oil and the pressure drop in the pipeline simultaneously byabout 3 percent each, or keeping the power constant, can increase theflow by about 6 percent.

The additives are miscible with the oil and do not change much as theoil is transported along the pipeline. This has been verified by severalhours run on the test flow loop. This means the probability ofdegradation as the oil is transported along a long pipeline is absent orminimal. This makes the additive mechanism very different fromconventional drag reducers, such as ultra-high molecular weightpolyalpha-olefins. It is important to the additive that the resin ispresent for the drag reducing additive to perform best.

Viscosity measurements were conducted with the following formulations,but they were not tested on the flow loop because of cost or otherreasons:

TABLE II Test Formulae Formulation No. Composition, wt % 1 100% Toluene2 100% isopropyl alcohol 3 100% butyraldehyde 4 100% Ethyl acetate 5100% acetonitrile 7 95% butyraldehyde 5% resin 8 47.5% Ethyl acetate,47.5% butyraldehyde, 5% resin 12 47.5% acetonitrile, 47.5% toluene, 5%resin 13 47.5% acetonitrile, 47.5% butyraldehyde, 5% resin

Many modifications may be made in the methods of and compositions ofthis invention without departing from the spirit and scope thereof. Forexample, different resins, esters, aldehydes, aromatic hydrocarbons,diluents, and different proportions may be used from those described orexemplified, and still be within the scope of the invention. Further,the drag reducing additives are expected to be useful in heavy oilsother than the specific ones exemplified herein.

The present invention may suitably comprise, consist or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed.

The words “comprising” and “comprises” as used herein throughout theclaims, are to be interpreted as “including but not limited to” and“includes but not limited to”.

1. A method of reducing the drag of oil through a conduit, the methodcomprising introducing to the oil an amount of a drag reducing additiveeffective to reduce the drag of oil through the conduit, the dragreducing additive comprising: a polymeric alkyl-substituted phenolformaldehyde resin; and a solvent selected from the group consisting ofan ester, an aldehyde, and combinations thereof.
 2. The method of claim1 where the effective amount of the drag reducing additive introduced tothe oil ranges from about 0.1 to about 2 vol % of the oil.
 3. The methodof claim 1 where the amount of polymeric alkyl-substituted phenolformaldehyde resin in the additive ranges from about 1 to about 20 wt %.4. The method of claim 1 where the alkyl group of the polymericalkyl-substituted phenol formaldehyde resin is a linear or branchedalkyl group having from 2 to 20 carbon atoms, and where the polymericalkyl-substituted phenol formaldehyde resin has a weight averagemolecular weight ranging from about 1,500 to about 30,000.
 5. The methodof claim 1 where the additive has a component selected from the groupconsisting of the following with the indicated proportions, based on thetotal solvent in the drag reducing additive: from about 10 to about 95wt % ester; from about 10 to about 95 wt % aldehyde; and combinationsthereof.
 6. The method of claim 1 where: the ester is selected from thegroup consisting of ethyl formate, methyl formate, methyl acetate, ethylacetate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyllactate, and combinations thereof; and the aldehyde is selected from thegroup consisting of formaldehyde, acetaldehyde, propionaldehyde,butyraldehyde, benzaldehyde, and combinations thereof.
 7. The method ofclaim 1 where the oil is diluted with from about 10 to about 30 vol % ofa diluent selected from the group consisting of condensate, naphtha,light crude oil, light synthetic crude oil and other light petroleumhydrocarbon fractions and combinations thereof.
 8. The method of claim 7where the oil containing the diluent and the additive have at least oneof the following improvements over an identical oil without theadditive: a viscosity reduction of at least 20%; a throughput increaseby at least 6%; a power consumption reduction by at least 3%; a diluentproportion reduction of at least 3%; and a combination thereof.
 9. Anoil having reduced drag through a conduit, the oil comprising: an oil; adiluent; and an effective amount of a drag reducing additive to reducethe drag of oil through the conduit where the drag reducing additivecomprises: a polymeric alkyl-substituted phenol formaldehyde resin; anda solvent selected from the group consisting of an ester, an aldehyde,and combinations thereof.
 10. The oil having reduced drag of claim 9where the effective amount of the drag reducing additive in the oilranges from about 0.1 to about 2 vol % of the oil having improved flow.11. The oil having reduced drag of claim 9 where the effective amount ofpolymeric alkyl-substituted phenol formaldehyde resin in the additiveranges from about 1 to about 20 wt %.
 12. The oil having reduced drag ofclaim 9 where the alkyl group of the polymeric alkyl-substituted phenolformaldehyde resin is a linear or branched alkyl group having from 2 to20 carbon atoms, and where the polymeric alkyl-substituted phenolformaldehyde resin has a weight average molecular weight ranging fromabout 1,500 to about 30,000.
 13. The oil having reduced drag of claim 9where the additive has a component selected from the group consisting ofthe following with the indicated proportions, based on the total solventin the additive: from about 10 to about 95 wt % ester; from about 10 toabout 95 wt % aldehyde; from about 10 to about 30 vol % of a diluentselected from the group consisting of condensate, naphtha, light crudeoil, light synthetic crude oil and other light petroleum hydrocarbonfractions and combinations thereof; and combinations thereof.
 14. Theoil having reduced drag of claim 9 where: the ester is selected from thegroup consisting of ethyl formate, methyl formate, methyl acetate, ethylacetate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyllactate, and combinations thereof; the aldehyde is selected from thegroup consisting of formaldehyde, acetaldehyde, propionaldehyde,butyraldehyde, benzaldehyde, and combinations thereof.
 15. The oilhaving reduced drag of claim 9 where the oil has at least one of thefollowing improvements over an identical oil without the additive: aviscosity reduction of at least 20%; a throughput increase by at least6%; a power consumption reduction by at least 3%; a diluent proportionreduction of at least 3%; and a combination thereof.